For folks who only occasionally or rarely have need of an compression/decompression program and are particular about what gets installed on their computer, I heartily recommend the portabilized version of Z-Zip, which is available either alone or can be rolled into a larger suite of tools from PortableApps.com.
All programs distributed from PortableApps are:
-Free. They cost nothing, don't give you pop-up reminders, aren't gimped (well, except for PortableGIMP, which is GIMPed, but in a good way).
-Opensource. All programs distributed from PortableApps can be modified and redistributed, and the source code is auditable.
-Portablized, which means no permanent registry changes. You can run them from portable media like a cd or a flash drive. You don't have to install them to run them, and you don't have to uninstall them to get rid of them. Just delete them when finished. Keep the suite on a spare flash drive and only plug it on on those .rar occasions when you need to use one of the programs in it.
Thanks to the I-Mod team for these handy posters, and the apparently even-more handy poster creator forthcoming. Merry Korxmas!
<edit> messy links, I'm used to using other forum markup language